Electric heating element



Nov. 17, 1953 M. IRELAND ELECTRIC HEATING ELEMENT Filed Sept. 20. 1950INVENTOR ATTORNEY latented Nov. l7, 195 3 UNITED STATES PATENT OFFICEELECTRIC HEATING ELEMENT Murray Ireland, Elgin, Ill., assignor to McGrawElectric Company, Elgin, 111., a corporation of Delaware This inventionrelates to electric heating elements for toasters the like, and isparticularly directed to an improved construction for securing theheating wire windings.

The electrical resistance wire windings, usually wire ribbon, of heatingelements, particularly when heating are likely to sag away from thesurface of the supporting form of the heating element. Various proposalshave heretofore been made for avoiding this difficulty but, so far as Iam aware, none of such proposals have been found practical.

The general object of t..-e present invention is to provide a heatingelement having the heating windings supported against sagging through asecuring construction which will not injure the windings or interferewith the heating effect thereof, and which is adapted for rapidproduction and otherwise acceptable for commercial employment.

According to the invention the windings of a heating element areanchored to the supporting form by individual securing means in the formof individual thin wire staples adapted to make substantially only pointor thin line contact with the heating ribbon or other wire, and furtherarranged to make merely sliding contact with the wire so as to avoidinjury thereto during the course of installation. Because of the closespacing usually employed between the windings of heating elements theuse of staples presents a difficulty in that if the staples be ofsufficiently small size to avoid short circuiting of adjacent windingsthey are likely to injure the heating wire in the course ofinstallation. According to the invention it is possible to use staplesof a size which can be employed without injury to the wire and whichwould cause short circuiting between adjacent windings if appliedcrosswise of the windings. To avoid the latter condition the staples arearranged in inclined relation to the windings. This permits the staplesfor the windings to be arranged in a line and permits installation ofthe staples by rapid machine methods.

The invention will be understood by reference to the accompanyingdrawing. In such drawing:

Fig. l is a front view of an electric heating element according to theinvention;

Fig. 2 is a corresponding rear view thereof; and

Fig. 3 is an enlarged sectional view taken at one of the securingstaples.

As conventionally, the flat electric insulating form it may comprisesheet mica, but it also 'may comprise other suitable insulatingmaterial.

taining relatively closely spaced notches i2 and i3. Metal eyelets l4and I5 are provided in the lower portion of the form for anchoring theends of the ribbon and providing electric terminals therefor. At the topof the form is metal clamping strip 16 having upstanding posts ll and i8adapted for the support of the heating element. Staples l9 secure theindividual windings of the ribbon against the form and will hereafter bemore fully described.

At the opposite edges of the form are notches i2 and i3. Asconventionally the spacing of adjacent notches may vary, preferablybeing more closely spaced in the lower area of the form to provide agreater concentration of heating wmdings of the ribbon therein than inthe upper area. The IlbbOll between windings extends through adjacentnotches i2 and I3 at the opposite edges of the form and is anchored byloop formations 20 and 2| at the back side of the form, as shown in Fig.2. Such loop formations are shown as containing an axial twist, but thisis not a part of my invention and is merely optional.

Staples l9 are of thin wire. The yoke thereof bridges an individualWlIldlIlg of the heating ribbon or other wire II and the staple legs 22extend through the form and are bent in anchoring engagement with theopposite face. As prevlously pointed out, it is desirable that thestaples be applied so as not to deform the wire. A light sliding contactbetween the staple and the heating wire is round suitable for securingpurposes. Accordingly, the staples must not be tightly clenched as inthe case or other usages.

It will be noted that the staples are relatively wide in relation to thespacing of the windings, and that if applied crosswise they would causeshort circulting. Accordingly they are arranged at a diagonal to thedirection of the windings. With such orientation the staples may bedisposed in a single line extending vertically to the heating elementand transversely to the direction of the windings. The particularheating element illustrated and described has the windings all disposedon the front face of the form. Certain leads of the wire, as shown inFig. 2 are disposed at the back of the form. These also may be socuredby staples 23 and 24 extending from back to front through the form inpositions which will not short circuit the windings. It will beunderstood that the invention i also applicable to heating elementshaving windings on both sides of the form.

Normally a single staple for each winding provides suilicient support,in which case the staples will preferably be located substantiallymidway between the opposite edges of the form. Where required, however,a plurality of staples may be employed at spaced point along eachwinding.

I claim:

1. An electric heating element comprising a flat electric insulatingform and an electric resistance wire having spaced straight windingsextending across the form and wire staples Wider than the wire of thewinding and contacting said wire securing the intermediate portions ofthe individual windings against one face of the form and extendingthrough and being anchored at the other face of the form, said staplesextending diagonally to the direction of the windings and adjacentstaples lying in spaced relation, and the legs of each staple beingspaced by an air gap from the winding secured by the staple.

2. An electric heating element comprising a flat electric insulatingform and an electric resistance wire having spaced straight windingsextending across the form and wire staples wider than the wire of thewindings and contacting said wire securing the individual windingsagainst one face or the form and extending through and being anchored atthe other face of the form, said staples extending diagonally to thedirection of the windings and said staples being arranged in a commonline transverse to the direction of the windings and adjacent stapleslying in spaced relation, the legs of each staple being spaced by an airgap from the winding secured by the staple.

3. In an electric heating element, in combination, a sheet of micahaving notches along a pair of opposite edges, a resistance wire lyingacross one face of said sheet of mica in spaced spans of straight wiresupported by engagement of looped portions of said Wire with saidnotches, and a row of wire staples wider than the wire of the spansextending through said sheet and clinched thereon, each of said staplesof the row straddling one of said spans intermediate its ends forsupporting it and with the legs of each staple being spaced by an airgap from the span which it holds, said staples lying at an acute angleto the wire of said spans and in parallel relation with each otherwhereby to provide spacing of the staple holding each span from adjacentspans and from the staples holding said adjacent span independently ofthe spacing between each span and said adjacent spans.

MURRAY IRELAND.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,359,400 Lightfoot Nov. 16, 1920 1,474,887 Bridges Nov. 20,1923 1,480,084 Lamb Jan. 8, 1924 1,565,539 Woodson Dec. 15, 19251,726,757 Murphy Sept. 3, 1929 2,040,369 Fischer May 12, 1935 2,243,993Watson June 3, 1941 2,419,355 Koci Apr. 22, 1947 2,503,601 Tice Apr. 11,1950 2,503,357 Ames May 23, 1950 2,522,724 Scharf Sept. 19, 19552,570,376 Quist Oct. 9, 1951

